Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

1. PublisherThe Goodheart-Willcox Co., Inc.Tinley Park, Illinois PowerPoint for Modern Automotive Technology by Russell Krick

2. Chapter 12 Engine Design Classifications

3. Contents • Engine classifications • Alternative engines • Typical automotive engines

4. Engine Classifications • Even though basic parts are the same, design differences can change the way engines operate and how they are repaired • For this reason, you must be able to classify engines

5. Common Engine Classifications • Cylinder arrangement • Number of cylinders • Cooling system type • Valve location • Camshaft location

6. Common Engine Classifications • Combustion chamber design • Type of fuel burned • Type of ignition • Number of strokes per cycle • Number of valves per cylinder • Type of aspiration

7. Cylinder Arrangement • Refers to the position of the cylinders in relation to the crankshaft • There are five basic cylinder arrangements: • inline • V-type • slant • W-type • opposed

8. Cylinder Arrangement

9. Number of Cylinders • Most car and truck engines have either 4, 6, or 8 cylinders • Some may have 3, 5, 10, 12, or 16 cylinders • Engine power and smoothness are enhanced by using more cylinders

10. Cylinder Numbering • Engine manufacturers number each engine cylinder to help technicians make repairs • Service manual illustrations are usually provided to show the number of each cylinder • Cylinder numbers may be cast into the intake manifold

11. Firing Order • Refers to the sequence in which the cylinders fire • Determined by the position of the crankshaft rod journals in relation to each other • May be cast into the intake manifold • Service manual illustrations are usually provided to show the firing order

12. Cylinder Numbering and Firing Order

13. Cooling System Type • There are two types of cooling systems: • Liquid cooling system • surrounds the cylinder with coolant • coolant carries combustion heat out of the cylinder head and engine block • Air cooling system • circulates air over cooling fins on the cylinders • air removes heat from the cylinders

14. Cooling System Type A. Air cooling B. Liquid cooling

15. Fuel Type • Engines are classified by the type of fuel used • Gasoline engines burn gasoline • Diesel engines burn diesel fuel • Liquefied petroleum gas (LPG), gasohol (10% alcohol, 90% gasoline), and pure alcohol can also be used to power an engine

16. Ignition Type • Two basic methods are used to ignite the fuel in an engine combustion chamber: • spark ignition (spark plug) • compression ignition (compressed air)

17. Spark Ignition Engine Uses an electric arc at the spark plug to ignite the fuel

18. Compression Ignition Engine Squeezes the air in the combustion chamber until it is hot enough to ignite the fuel

19. Valve Location • Engines are classified by the location of the valves: • L-head engine • also called a flat head engine • I-head engine • also called an overhead valve (OHV) engine

20. L-Head Engine Both the intake and exhaust valves are in the block

21. I-Head Engine Both valves are in the cylinder head

22. Camshaft Location • There are two basic locations for the engine camshaft: • Camshaft located in the block • cam-in-block engine • Camshaft located in the cylinder head • overhead cam (OHC) engine

23. Cam-in-Block Engine • Uses push rods to transfer motion to the rocker arms and valves • Also called an overhead valve (OHV) engine

24. Overhead Cam Engine Camshaft is located in the top of the cylinder head

25. Overhead Cam Engine • OHC engines may use one or two camshafts per cylinder head • Single overhead cam (SOHC) engine • uses only one camshaft per cylinder head • Dual overhead cam (DOHC) engine • uses two camshafts per cylinder head • one cam operates the intake valves, while the other cam operates the exhaust valves

26. Combustion Chamber Shape • Four basic combustion chamber shapes are used in most automotive engines: • pancake • wedge • hemispherical • pent-roof

27. Pancake Combustion Chamber • Chamber forms a flat pocket over the piston head • Valve heads are almost parallel to the top of the piston

28. Wedge Combustion Chamber • The valves are placed side-by-side • The spark plug is located next to the valves • When the piston reaches TDC, the squish area formed on the thin side of the chamber squirts the air-fuel mixture out into the main part of the chamber • this improves air-fuel mixing at low engine speeds

29. Wedge Combustion Chamber Provides good air-fuel mixing at low engine speeds

30. Hemispherical Combustion Chamber • Shaped like a dome • The valves are canted on each side of the combustion chamber • The spark plug is located near the center of the chamber, producing a very short flame path for combustion • The surface area is very small, reducing heat loss

31. Hemispherical Combustion Chamber • First used in high-horsepower racing engines • Excellent design for high-rpm use

32. Pent-Roof Combustion Chamber • Similar to a hemispherical chamber • Has flat, angled surfaces rather than a domed surface • Improves volumetric efficiency and reduces emissions

33. Pent-Roof Combustion Chamber

34. Other Combustion Chamber Types • In addition to the four shapes just covered, there are several less common combustion chamber classifications • Each type is designed to increase combustion efficiency, gas mileage, and power while reducing exhaust emissions

35. Swirl Combustion Chamber Causes the air-fuel mixture to swirl as it enters the chamber, improving combustion

36. Four-Valve Combustion Chamber Uses two exhaust valves and two intake valves to increase flow

37. Three-Valve Combustion Chamber • Uses two intake valves and one exhaust valve • Two intake valves allow ample airflow into the combustion chamber on the intake stroke • Single exhaust valve provides enough surface area to handle exhaust flow

38. Stratified Charge Combustion Chamber • Uses a small combustion chamber flame to ignite and burn the fuel in the main, large chamber • Lean mixture is admitted into the main chamber • Richer mixture is admitted into the small chamber by an extra valve

39. Stratified Charge Combustion Chamber • When the mixture in the small chamber is ignited, flames blow into the main chamber and ignite the lean mixture • Allows the engine to operate on a lean, high-efficiency air-fuel ratio • fuel economy is increased • exhaust emissions are reduced

40. Air Jet Combustion Chamber • Has a single combustion chamber fitted with an extra air valve, called a jet valve • The jet valve injects a stream of air into the combustion chamber at idle and at low engine speeds to improve fuel mixing and combustion • At higher rpm, normal air-fuel mixing is adequate for efficient combustion

41. Air Jet Combustion Chamber

42. Precombustion Chamber • Commonly used in automotive diesel engines • Used to quiet engine operation and to allow the use of a glow plug to aid cold weather starting • During combustion, fuel is injected into the prechamber, where ignition begins • As the fuel burns, the flame expands and moves into the main chamber

43. Precombustion Chamber

44. Alternative Engines • Vehicles generally use internal combustion, 4-stroke cycle, reciprocating piston engines • Alternative engines include all other engine types that may be used to power a vehicle

45. Rotary Engine • Uses a triangular rotor instead of pistons • The rotor orbits a mainshaft while turning inside a specially shaped chamber • This eliminates the reciprocating motion found in piston engines

46. Rotary Engine

47. Rotary Engine Operation • Three complete power-producing cycles take place during every revolution of the rotor: • three rotor faces produce three intake, compression, power, and exhaust events per revolution

48. Rotary Engine Operation • Rotor movement produces a low-pressure area, pulling the air-fuel mixture into the engine • As the rotor turns, the mixture is compressed and ignited • As the fuel burns, it expands and pushes on the rotor • The rotor continues to turn, and burned gases are pushed out of the engine

49. Rotary Engine Operation

50. Steam Engine • Heats water to produce steam • Steam pressure operates the engine pistons • Known as an external combustion engine since its fuel is burned outside the engine